Composed in 1827, when Mendelssohn was 18 years old, this sonata is frequently performed and well-loved among Mendelssohn's sonatas. The first edition was published posthumously in 1868. The opus number was assigned by publishers and editors after Mendelssohn's death and therefore does not correspond to the order of composition.

Mendelssohn held Beethoven in high esteem. Even in this work, composed in 1827, the year of Beethoven's death, many similarities to Beethoven's Hammerklavier Sonata have been noted. It consists of four movements and is performed in its entirety. The average performance time is just under 20 minutes.

First Movement: B-flat Major, Allegro vivace

It opens with a brilliant and powerful ascent featuring repeated double stops. It shares a very similar character with the Hammerklavier Sonata. The crisp rhythmic motif from the opening permeates the entire movement, providing a sense of unity.

Second Movement: B-flat Minor, Scherzo

In three-part form. A scherzo movement where sixteenth notes are played lightly and staccato throughout. While generally crisp, the sustained notes and short phrases connected by slurs within it create an impressive effect.

Third Movement: E Major, Andante quasi Allegretto – Allegro molto

In three-part form. A graceful melody is sung in octaves over a floating rhythmic accompaniment in 6/8 time. The middle section is short and has a somewhat melancholic atmosphere. After the original theme reappears, a short coda emerges, leading into the Allegro molto. This section has a transitional character and incorporates the rhythmic motif from the first movement. It gradually builds excitement, leading into the fourth movement.

Fourth Movement: B-flat Major, Allegro moderato

Played without a break from the third movement. In three-part form. A gentle melody is played by the right hand, supported by a triplet accompaniment in the left hand. In the middle section, marked Allegro non troppo, the atmosphere changes completely, and material from the second movement's scherzo is reused. The opening theme is then recapitulated, and after a harmonic build-up, the melody played in octaves is exceptionally sweet and captivating. Finally, a soft atmosphere is created with arpeggios, and the piece concludes as if fading away.